Method of making fluid-conducting hot-forging die

ABSTRACT

A foraminous ordinary-duty-hot-forging die is provided with minute fluid passageways therethrough for the conduction of a coolant, a lubricant or a protective atmosphere under high pressure. A porous hot-forging die is made by forming a briquette of coarse powdered tool metal or carbide, sintering the briquette, machining a die cavity or die bore therein, and heattreating the thus-formed die for the required hardness and wear resistance. A modified heavy-duty-fluid-conducting hot-forging die is formed from powdered material by loading the die cavity of a briquetting press with a charge consisting of alternate layers of powdered tool metal or carbide and fusible wire inserts extending thereacross and compressing this charge into a briquette. This briquette is then sintered at a temperature below the melting point of the insert material, hot-forged to densify it so as to produce a substantially solid die forging of approximately 100 percent density, annealed, and bored to form a central pilot hole therethrough. The die forging is then vacuum-sintered at a temperature higher than the melting point of the insert material with a sufficiently low vacuum to vaporize the insert material and withdraw it from the body, leaving perforations therethrough. The sintered perforated die forging is then machined to provide the desired shape of die cavity or die bore and finally heattreated to obtain the necessary hardness and wear resistance. Either form of die is mounted in a bore in a die-holding block having a chamber therearound. During hot-forging operations, this chamber is supplied with a coolant, a lubricant or a protective atmosphere agent under a sufficiently high pressure to force it through the pores of the porous die or through the perforations in the solid die while the die is being used to hot-forge, extrude or otherwise form workpieces.

ilit tates aterit 91 Haller Primary Examiner-Harrison L. MinsonAttorney-Barthel and Bugbee [57] ABSTRACT A foraminousordlnary-duty-hot-forging die is provided with minute fluid passagewaystherethrough for the conduction of a coolant, a lubricant or aprotective atmosphere under high pressure. A porous hotforging die ismade by forming a briquette of coarse and heat-treating the thus-formeddie for the required hardness and wear resistance.

A modified heavy-duty-fluid-conducting hot-forging die is formed frompowdered material by loading the die cavity of a briquetting press witha charge consisting of alternate layers of powdered tool metal orcarbide and fusible wire inserts extending thereacross and compressingthis charge into a briquette. This briquette is then sintered at atemperature below the melting point of the insert material, hot-forgedto densify it so as to produce a substantially solid die forging ofapproximately 100 percent density, annealed, and bored to form a centralpilot hole therethrough. The die forging is then vacuum-sintered at atemperature higher than the melting point of the insert material with asufficiently low vacuum to vaporize the insert material and withdraw itfrom the body, leaving perforations therethrough. The sinteredperforated die forging is then machined to provide the desired shape ofdie cavity or die bore and finally heat-treated to obtain the necessaryhardness and wear resistance. Either form of die is mounted in a bore ina die-holding block having a chamber therearound. During hotforgingoperations, this chamber is supplied with a coolant, a lubricant or aprotective atmosphere agent under a sufficiently high pressure to forceit through the pores of the porous die or through the perforations inthe solid die while the die is being used to hot-forge, extrude orotherwise form workpieces.

4 Claims, 12 Drawing Figures PATENTEI; W29 I975 SHEET 1 BF 3 INVENTOR 46JOHN HALLER BY W-25L ATTORNEYS PATENTEU 3.735.648

SHFET 3 0F 3 INVENTOR JOHN HALLER BY @WW WQL ATTORNEYS METHOD OF MAKINGFLUID-CONDUCTING HOT-FORGING DIE This is a division of my co-pendingapplication, Ser. No. 875,975, filed Nov. 12, 1969, for Fluid-ConductingHot Forging Die and Method of Making the Same.

BACKGROUND OF INVENTION Hitherto, hot-forging dies of solid metal havepossessed short working lives and have been subject to considerableoxidation as a result of the high pressures and high temperatures towhich they have been subjected during use. The present invention enablesan ordinary-duty die to be formed from powdered metal or carbide withpores sufficiently large for the passage of a coolant, a lubricant or aprotective atmosphere agent, increasing the working life of the die. Thesubstantially solidified sintered powdered metal perforated heavydutyhot-forging die of the modification of the invention enables highertemperatures and higher forging pressures to be employed yet withincreased working life than in previous hot-forging dies. 7

In the drawings:

FIG. I is a central vertical section through an ordinary-dutyfluid-conducting hot-forging die of sintered powdered metal or carbide,according to one form of the invention;

FIG. 2 is a central vertical section through a hotforging or extrusionpress showing the hot-forging die of FIG. I at the start of ahot-forging or extrusion operation;

FIG. 3 is a view similar to FIG. 2, but showing the position and shapeof the workpiece at the conclusion of the hot-forging or extrusionoperation;

FIG. 4 is a central vertical section through a heavydutyfluid-conducting hot-forging die of densit'red sintered powdered metalor carbide, according to a modification of the invention;

FIG. 5 is a top plan view of a fusible wire insert employed in making aheavy-duty solidified hot-forging die, according to a modification ofthe invention as shown in FIG. 4;

FIG. 6 is a central vertical section through the die bore of abriquetting press showing the formation of the briquette for the heavyduty die of FIG. 4 at the start of the briquetting operation;

FIG. 7 is a view similar to FIG. 6 but showing the briquette at the endof the briquetting operation;

FIG. 8 is an enlarged central vertical section'through the pre-sinteredbriquette of FIG. 7 after a pilot hole has been drilled therethrough;

FIG. 9 is a cross-section taken along the line 9-9 in FIG. 8;

FIG. 10 is a central vertical section through a hotforging or extrusionpress showing the hot-forging die of FIG. 4 at the start of ahot-forging or extrusion operation;

FIG. 11 is a fragmentary cross-section taken along the line 11-11 inFIG. 10; and

FIG. 12 is a view similar to FIG. 10 but showing the shape and positionof the workpiece at the conclusion of the hot-forging or extrusionoperation.

Referring to the drawings in detail, FIG. 1 shows a porous ordinary-dutyhot-forging die, generally designated 20, according to one form of theinvention, as consisting of a porous body 22 of sintered powdered metalor carbide preferably with a slightly tapered side surface 24 and withtop and bottom surfaces 26 and 28 respectively interconnected by a diecavity 30. The die cavity 30 is shown by way of example to have a shapeadapted for the production of a poppet valve workpiece 32 (FIG. 3), suchas is used in the manufacture of internal combustion engines and in thisinstance consists of an approximately cylindrical upper cavity 34, atapered intermediate bore 36 and a straight cylindrical lower bore 38.

The body 22 is first formed as a briquette or compact by conventionalbriquetting or compacting methods and apparatus known to those skilledin the powder metallurgy art, using a preponderance of a coarse metal orcarbide powder, such as 150 mesh tool steel, or tungsten carbide,titanium carbide or silicon carbide powder with or without the additionof a finer mesh powder thereof, depending upon the porosity desired forthe die. This powder is mixed with other necessary ingredients, such asgraphite, and a lubricant in order to obtain a homogeneous blend of thecomponent ma terials possessing the proper chemical composition. Thecharge of this powder mixture is placed in a conventional briquetting orcompacting press and compacted at a pressure higher than the pressure towhich the die is expected to be subjected in service. For example, ifthe die 20 is expected to be used in hotforging service at pressures notexceeding 50 tons per square inch, it would be compacted at a pressureof about tons per square inch.

The compact or briquette is then removed from the briquetting press andsintered in the conventional manner for the particular die materialemployed, and in a protective atmosphere, such as a hydrogen ordissociated ammonia atmosphere if oxidizable ingredients, such aschromium, are present. After the briquette has been sintered, it isbored or otherwise machined to form the die cavity or die bore 30 withthe shape required for the production of the particular workpiece 32 tobe produced. The die 20 thus formed is heattreated in a conventionalmanner to provide it with the necessary hardness and wear resistance.If, during machining, the porosity of the die body 22 has been impaired,such as by wholly or partially closing up the pores, these may bere-opened by the use of a conventional chemical etching agent.

The porous hot-forging die 20, thus produced, is mounted in aconventional hot-forging or extrusion press or machine, generallydesignated 46, shown diagrammatically in FIG. 2. This is shown, in itsworking parts adjacent the die 20, to include a press bed assembly 42consisting of a lower punch support 44 mounted on a lower bolster plate(not shown), a back-up plate 46 resting on the lower punch support 44,and a die holder plate 48 disposed above the back-up plate 46. The lowerpunch back-up plate 46 is provided with a stepped bore 50 in which ismounted a correspondingly flanged lower punch 52 containing an elongatedcentral bore 54. The bore 54 slidably receives the upper end portion ofan ejector or knockout rod or plunger 55 and opens into an enlarged bore56 in the lower punch support 44, which contains a counterbore 58 snuglyreceiving the lower portion and lower end of the lower punch 52, whichhas an upper end surface 60 upon which the lower end surface 28 of thedie 20 rests.

The die holder plate 4% contains a bore 62 which is tapered according tothe taper of the side surface 24 of the die 20 so as to fit snuglytherewith. Intermediate the opposite ends of the tapered bore 62 thereare provided upper and lower annular passageways 64 and 66 respectivelyinterconnected by circumferentially spaced fluted fluid transmissiongrooves 68, similar to those shown in FIG. 11. Extending outward throughthe body 70 of the die holder plate 48 is a passageway 72, the outer endof which is threaded to receive the correspondingly threaded highpressure coupling 74 connecting the passageway to a high-pressureconduit 76 which at its opposite end is connected by a high pressureelbow coupling 78 to a high pressure fluid accumulator, generallydesignated 80. The accumulator 80 is adapted to contain a lubricant, acoolant or a protective atmosphere agent subjected to a standingpressure indicated on a pressure gauge 82 communicating therewith by aTee fitting 84 which in turn is connected to a conduit 86 leading to apressure-regulated pressure source (not shown).

The hot-forging or extrusion press or machine 40 also includes an upperplaten or ram 88 (FIG. 2) which is provided with a socket 90 receivingthe upper or butt end 91 of an upper punch 92 having a lower end surface94 with a nose portion 95 thereon and also having an annular taperedportion 96 thereon urged toward the upper platen 88 by its engagementwith the correspondingly tapered bore 98 in a retaining plate or ring 99bolted or otherwise secured to the upper platen 88.

In the operation of the hot-forging or extrusion press or machine 40employing the ordinary-duty fluidconducting hot-forging die 20, let itbe assumed that the upper platen 88 and upper punch 92 have been movedupward to their retracted positions so as to leave open for loading thedie cavity 30 in the hotforging die 20. Let it also be assumed that thelatter and its die holder 70 and back-up plate 46 have been heated to asuitable pre-heating temperature between 600 F. and 1,000 F. byconventional means (not shown). Let is also be assumed that theaccumulator 80 has been placed in operation to cause a flow of coolantor lubricant, as the case may be, through the passageway 72 into thechamber 68 whence this fluid surrounds the body 22 of the hot forgingdie 20 and penetrates the pores thereof to reach the die cavity 30. Thiscontemplates the use of a pressure within the range of 100 pounds persquare inch up to 5,000 pounds per square inch, depending upon the sizeof the pores in the die body 22 and the viscosity of the fluid beingtransmitted therethrough.

A workpiece slug or blank B having been heated to a suitable forgingtemperature, is now dropped into the die cavity 30 of the now-heatedporous hot-forging die 20 and the platen 88 then made to descend,causing the upper punch 92 to enter the upper portion 34 of the diecavity 30. The lower end 94 and the nose portion 95 thereof engage thehot slug or blank B and push it downward, causing the material thereofto undergo flow and to be extruded through the tapered intermediate bore36 into the straight cylindrical lower bores 38 and 54 (FIG. 3). Theforegoing action forms a workpiece W having a head H with a recess R andan elongated stem S interconnected by a tapered neck N. It will beunderstood, however, that the workpiece W is merely one form ofworkpiece which may be hotforged by the porous die 20 of the presentinvention and that many other forms of workpiece may also be hot-forgedthereby in a similar manner according to the configuration of theworkpiece W and the consequent shape of the die cavity 30 required toproduce it.

The upper platen 88 and punch 92 are now retracted upward away from thedie cavity 30. The workpiece W, which for purposes of illustration hasbeen illustrated and described as for a poppet valve for an internalcombustion engine, is now caused to be ejected from the die cavity 30 bymoving the ejector rod or plunger 55 upward in the bore 54 so as toengage the lower end of the workpiece W and first dislodge it and thenpush it upward out of the die cavity 30. Meanwhile, the high pressurecoolant or lubricant fluid reaching the die cavity 30 through theconduit 72, chamber 68 and pores of the die body 22 cools or lubricates,or both cools and lubricates the wall of the die cavity 30 and alsocools the hot-forging die 20, inhibiting oxidation, deterioration andwear and greatly increasing the life of the die 20. In the alternative,a gaseous protective agent reaching the die cavity 30 through the poresof the die body 88 from the passageway 72 and chamber 68 preventsoxidation of the heated workpiece slug or blank B and the workpiece Wforged or extruded therefrom.

The modified heavy-duty fluid-conducting hotforging die, generallydesignated 100, shown in FIG. 4 is also adapted to be cooled, lubricatedor supplied with a protective atmosphere but is employed for heavydutyhot-forging where the pressures involved are beyond the capacity of theporous ordinary-duty hotforging die 20 of FIGS. 1, 2 and 3. Unlike theporous hot-forging die 20 of porous sintered powdered material, thedensified fluid-conducting hot-forging die is composed of sinteredpowdered material which has been subjected to hot-forging itself inorder to compress its particles, close up its pores and densify it so asto render it substantially solid with a density approaching 100 percent.Instead of the fluid-conducting pores of the porous die 20 of FIG. 1,the heavy-duty die 100 of FIG. 4 is provided with elongated minutefluidconducting passageways or channels 102 extending from its externalsurface 104 to its die cavity 106 through its body 108.

To produce the densified substantially solid hotforging die 100,powdered material, such as powdered metal or powdered carbide, withconventional sizes of particles is briquetted or compacted in aconventional briquetting press 112 shown diagrammatically in FIGS. 6 and7. The briquetting press 112 is shown as including a briquetting die 114containing a briquetting die cavity or bore 116 with a lower punch 118entering the lower end thereof and an upper punch 120 movable into andout of the upper end thereof.- The upper punch 120 movable into and outof the upper end thereof. The upper punch ,120, like the upper punch 92of FIG. 2, is connected to an upper platen (not shown) which, at thestart of operation, is retracted upward away from the briquetting die114. The die cavity 1 16 is then filled with a charge 122 consisting ofalternate layers 124 and 126 of metal or carbide powder and fusibleinserts respectively.

Each fusible insert 126 (FIG. 5) possesses the configuration of thepattern of holes or perforations desired in the finished die 104 andconsists of multiple fusible wire arms 128 arranged in a wheel-spoke orstarshaped pattern and secured at their midportions to one another inany suitable manner as by solder 130. The inserts 126 are convenientlyformed from copper wire because of its ease of soldering and convenientmelting point of 1,980 E, but it will be understood that other suitablefusible materials may also be employed for this purpose. The powderlayers 124 of the charge 122 are conveniently composed of so-called highspeed steel or tool steel powder or of carbide powder, such as tungstencarbide, titanium carbide or silicon carbide. The loading of thebriquetting die cavity 116 with the charge 122 is performed by placingthe lowermost layer 124 of powder on the top surface 132 of the lowerpunch 118, whereupon an insert 126 is placed on top of the powder layer124. A second layer 124 of powder is then placed on top of the firstinsert 126, followed by another insert 126 in a slightly rotatedposition (FIG. 9) and so forth until the die cavity 116 is filled to theextent necessary to produce the desired size of die 100 with the arms120 of the inserts 126 offset relatively to one another in differentlayers of the charge 122 (FIG. 9).

The briquetting press 112 is then operated to cause the upper punch 120to descend and enter the die cavity 116 (FIG. 6), compressing the charge122 therein (FIG. 7). Meanwhile, the lower punch 118 is held stationaryor, if the die 114 is mounted upon a conventional die cushion (notshown), the assembly of die 114 and lower punch 1 descends slightly. Theresult is the compressed insert-equipped briquette 134 shown in FIG. 7.The upper punch 120 is then retracted upward, whereupon the briquette orcompact 134 is ejected from the briquetting die cavity 116 by moving thelower punch 118 upward.

The briquette or compact 134 is then pre-sintered in a suitableatmosphere such as hydrogen or dissociated ammonia at a temperaturesufficiently below the melting temperature of the inserts 126 to preventmelting thereof yet at the same time sufficient to pre-sinter the entirebriquette 134, The pre-sintered briquette is then normally re-heated tothe presintering temperature to still avoid melting the inserts 126 andis then sub 'pcted to hot-forging to convert the pre-sintered compactinto a substantially solid die forging 140 (FIG. 0) approaching 100percent density. in the alternative, the hot working of the forging 140can also be accomplished without reheating if the pre-sintered compactis removed quickly from the pre-sintering furnace and hotforgedimmediately before it has had time to cool. The forging operation uponthe sintered compact distorts v the cross-section shape of the inserts126 very slightly from their original shape, thereby converting thewires 120 from circular cross-section to approximately ovalcross-section.

The hot-forged sintered compact or die forging 140 is then annealed in aconventional manner to soften it sufficiently to permit the drilling ofa central pilot hole 136 (FIG. 0), whereupon the insert-equipped forging140 is then fully sintered in a vacuum at 2,000 F. to 2,500 F.,depending upon its material. This action melts and vaporizes thematerial of the inserts 126 and withdraws it by suction, leaving theperforated hotforging die blank forging 140 (FIG. 0) provided with theholes, passageways or channels 102 radiating outward from the pilot bore136 to the external surface 144 of the die blank 140. If the inserts 126aremade from copper wire which has a melting point of l,980 F thehot-forging is performed at approximately l,900 F. and a one-micronvacuum at a temperature or 2,100 F. melts, vaporizes and removes thecopper material of the inserts 126.

The die forging 140 thus equipped with multiple passageways 102 is nowmachined to form the heavy-duty substantially solid fluid-conductinghot-forging die 100 by boring or otherwise producing its die cavity 106.This die cavity or die bore 106 can also be produced by so-calledelectrical discharge machining and can be of any suitable configuration.The particular die cavity 106 shown in FIG. 4 is presented solely by wayof example for fonning a poppet valve workpiece similar to the workpieceW shown in FIG. 3. In the event that the mouths of the perforations orpassageways 102 become partially or wholly clogged during the machiningoperation which produces the die cavity 106, these openings can becleared by the use of a conventional etching agent, such as an etchingacid.

In the use of the perforated heavy-duty die 100, the latter is mountedin a conventional hot-forging or extrusion press or machine, generallydesignated 140, shown diagrammatically in FIGS. 10, 11 and 12 andincludes a press bed assembly 150 having a lower punch 152 mounted in alower punch back-up plate 153 above a lower bolster plate (not shown) ina manner similar to the arrangement shown in FIGS. 2 and 3. An outer die154 is provided with a tapered outer surface 156 and is mounted in thecorrespondingly tapered bore 158 of a pre-stressed annular die holder160 which in turn is provided with a tapered outer surface 162 mountedin a tapered bore 164 in a die holder plate 166.

The outer die 154 is provided with an upper die bore 168 snuglyreceiving an upper punch 170 and is also provided with a counterbore 172snugly receiving the outer surface 100 of the die 100 at its upper andlower ends. The counterbore 172 intermediate its upper and lower ends isprovided with a pair of vertically spaced annular upper and lower fluidpassageways 174 and 176 interconnected by grooves 178 (FIG. 11)extending therebetween and sufficiently therebeyond to reach all of thepassageways 102 in the die 100. From the lower annular fluid passageway176 a fluid passageway 100 extends upward within the outer die 154 andat its upper end is threaded to receive a high pressure elbow fitting102 connected to the coupling 104 of a high pressure fluid supply line136.

The operation of the hot-forging or extrusion press 146 employing theperforated solid hot-forging die 100 is sufficiently similar to that ofthe hot-forging or extrusion press or machine 40 described above as torequire no repetition, hence is not repeated in order to avoidduplication. The high pressure fluid reaching the annular passageways176 and 174 by way of the passageway 100 and elbow coupling 132, 104from the high pres sure fluid line 186, whether a coolant, a lubricantor a protective agent, passes through the minute perforations orpassageways 102 in the hot-forging die 100 and c'ools, lubricates orprotects both the die 100 and the workpiece therein (FIG. 12) as theheated slug or blank B is forced downward through the die cavity or diebore 106 to become the elongated workpiece W. The upper punch 170 isthen retracted upward and the knockout rod or ejection plunger (notshown, but similar to the member 55 in FIGS. 2 and 3) is then movedupward to eject the workpiece W from the die cavity 106 and die bore168.

I claim: I

1. A method of making a fluid conducting hotforging die, comprisinghigher than the melting temperature of said inserts but lower than themelting temperature of said powdered material.

2. A method, according to claim 1, including the additional steps offorming a pilot bore in aid pre-sintered body following densificationthereof, and applying suction to said pre-sintered body during sinteringthereof to withdraw the melted insert material therefrom.

3. A method, according to claim 2, including the additional step ofannealing the pre-sintered body prior to forming the pilot bore therein.

4. A method, according to claim 1, including forming said die bodyinserts with radially disposed portions crossing one another andsecuring said portions to one another at their crossing points.

2. A method, according to claim 1, including the additional steps of forming a pilot bore in said pre-sintered body following densification thereof, and applying suction to said pre-sintered body during sintering thereof to withdraw the melted insert material therefrom.
 3. A method, according to claim 2, including thE additional step of annealing the pre-sintered body prior to forming the pilot bore therein.
 4. A method, according to claim 1, including forming said die body inserts with radially disposed portions crossing one another and securing said portions to one another at their crossing points. 